1. Field of Invention
The present invention relates to a package structure. More particularly, the present invention relates to a package structure with embedded electronic devices.
2. Description of Related Art
The integrated circuit chips (IC chips) are required to offer powerful functions as the electronic products develop toward multi-functions and high speed signal transmission. Moreover, more passive devices are demanded for consumer electronic products. However, under the developing trends of electronic products for miniaturization, lightweight, and low cost, the IC packaging industry is concerned about how to accommodate numerous electronic components or devices in the limited packaging space. In order to meet the above requests, system in package (SIP) packages, including multi-chip module (MCM) packages, are proposed by employing key technologies of the embedded technology and the surface buildup technology. The package structure either can be significantly diminished by embedding electronic devices therein, or may pack up more electronic devices through the embedded technology. The surface buildup technology can increase the circuit density and decrease the device thickness, thus improving the packaging compactness.
However, the yield of the package structure employing the surface buildup technology keeps decreasing as more buildup layers are formed one after another, especially for high pin count chips with additional buildup layers. In order to increase the yield and production and decrease the process complexity, multiple circuit boards are pressed together all at one time, as proposed in U.S. Pat. No. 6,828,221. However, as the pressing process exerts quite large pressure, it is rarely used for directly pressing chips and the substrate together. On the other hand, U.S. Pat. No. 6,759,270 proposed to form a circuit redistribution structure before pressing the multi-layered circuit board and chips together, so as to avoid directly pressing the chips. In addition, in U.S. Pat. No. 6,469,374, the chips are mounted to the board before pressing multiple boards together. Still, considerable issues of broken chips due to overlarge pressing stress exist in these processes.